Flow dividing system



Nov; 27,' 1962 J. CURLETT FLOW DIVIDING SYSTEM INVENTOR ATTORNEYS Jo/m Curl'eff Filed Dec. 2, 1960 HUM 6 u G a I l I i III III Unite States a 3,065,602 FLOW DIVIDING SYSTEM John Curiett, Los Gatos, Calif, assignor to Gurries Manufacturing (10., a corporation of California Filed Dec. 2, 1960, Ser. No. 73,379 4 Claims. (Cl. 60-52) This invention relates to a flow dividing system, and particularly to one which has been especially developed to serve the level-adjusting requirements of a road grader or builder, such as that shown in copending application of Raymond A. Gurries and myself, Serial No. 787,496, filed January 19, 1959, and now Patent No. 3,000,122.

The control structure for the leveling of the grading blade of the road builder shown in said application included a conventional gearatype flow divider which, however, was found to be inadequate for the purpose for various reasons inherent in the structure of such a divider.

It is therefore the principal object of the present invention to provide a flow dividing system which avoids the inadequacies of the above identified type of flow divider and instead gives extremely accurate equal and sensitive control of the hydraulic cylinders or rams actuated by the system.

A further object of the invention is to provide a flow dividing system which can be arranged to control or actuate more than a'pai-r of rams with equal efliciency and accuracy.

Still another object of the invention is to provide a flow dividing system which makes use of a number of standard or conventional units in its make-up, without the necessity of any specially designed parts being necessary other than a mounting housing or supports for the units, and which is arranged so that any such unit may be easily removed for repairs or replacement if necessary without disturbing the other units.

Another object of the invention is to provide a practical, reliable, and durable flow dividing system, and one which will be exceedingly effective for the purpose for which it is designed.

These objects are accomplished by means of such structure and relative arrangement of parts as will fully appear by a perusal of the following specification and claims.

In the drawings:

FIG. 1 is a front elevation of the flow dividing assembly of the system, with the enclosing cover for the drive elements of the assembly.

FIG. '2 is a transverse sectional elevation on line 22 of FIG. 1.

FIG. 3 is a flow diagram of the system.

Referring now more particularly to the drawings, and to the characters of reference marked thereon, the system as here shown comprises a pair of identical hydraulic pumps 1 and 2 of constant-displacement piston type, such as can be purchased in the open market. Each pump includes an enclosing housing 3 and a drive shaft 4 projecting from one end thereof.

To drive the pumps, a conventional constant delivery hydraulic piston-type motor 5 is provided; this motor also including a housing 6 and a driven shaft 7 projecting from one end thereof.

The housings of the pumps and motor are removably secured, by means of bolts or cap screws 8, against one face of a heavy mounting plate 9 so that the housings are spaced apart from each other somewhat and so that the shafts 4 and 7 all project through the plate and beyond the opposite face thereof, as shown in FIG. 2.

The pumps 1 and 2 are driven at the same speed by the motor 5 by suitable means, such as sprockets It) on the projecting ends of the pump shafts 4 (all the sprockets being in a common plane), a sprocket 11 on the corresponding end of the motor shaft 7, and an endless drive chain 12 extending about and engaging all the sprockets in driving relation, as shown in FIG. '1.

In order to protect and enclose the sprockets and chain and enable the same to be maintained in a properly lubri cated condition, a cover 13 is placed over the same; said cover including a peripheral flange or skirt 14 having a sealing gasket or ring 15 about its outer edge to engage the adjacent face of the mounting plate 9, which is of a size such that its peripheral edge is some distance outwardly of the sprocket engaging chain. The cover is held in place against the plate 9 by means of removable cap screws 16. The plate 9 is adapted to be rigidly mounted on the road builder or other machine at a suitable point thereon and so that the ends of the pumps and motor opposite the plate 9 are exposed for connection to the necessary piping. This is preferably done by means of an ear 17 rigid with and projecting from said plate 9; said ear having holes 18 through which securing bolts may project.

The pumps and motor are thus arranged as a compact rigid unit, and the pumps -1 and 2 are connected to a source of fluid pressure, and to the separate rams 19 and 20 respectively, actuated by said pumps, in the following manner:

Mounted on the road builder, or other machine, at any suitable point thereon is a constantly driven pump 21, the output or pressure conduit 22 of which extends to connection with a branch conduit 23, the ends 24 and 25 of which are connected to the intake or suction side of the pumps 1 and 2, respectively. The output or pressure conduits 26 and 27 of pumps 1 and 2 lead to the rams 19 and 20, respectively. A lateral conduit 28 from conduit 22 leads to the motor 5 to drive the same, the return conduit 29 from the motor leading back to a supply tank 30. A conduit 31 leads from the tank to the intake side of pump 21.

Interposed in conduit 22 between the pump 21 and conduit 28 is a control valve 32 which may be manually actuated, but is preferably one controlled and actuated by ground or road bed undulations, as shown in US. Patent No. 2,883,777. This valve is adapted to be disposed so as to feed fluid from pump 21 to pumps 1 and 2, or so as to direct the fluid from said pumps 1 and 2 back to the tank 30 through a return conduit 33.

As is usual in any constantly-operating pressure pumping systems, a relief conduit 34 leads to the tank 30 from the conduit 22 at a point thereon between the pump 21 and the valve 32.

With the above described arrangement of mechanical units and conduits, it will be found that a flow dividing system has been provided which meets the requirements of a flow divider. These requirements are:

(1) That the rams will receive the same amount of fluid regardless of the work pressure, so that both rams will be actuated to the same extent.

(2) That when the control valve, however, actuated, is in the off or closed position, the intake and return sides of the conduit system will be isolated from each other so as to hold the load on the rams without the possibility of leakage from the high to the low pressure side of the divider.

('3) That the flow will be divided when moving in one direction and will be recombined when moving in the reverse direction.

(4) That a pulsating up and down flow can be handled without causing any drift in the phase of the rams controlled by the system.

(5) That the flow may be split more than two ways (or fed to more than two rams) without loss of efliciency.

The gear type flow dividers at present available do not meet the above requirements. They have very high internal leakage or bypassing around the gears, which of course detracts from their effectiveness and volumetric efliciency, and it is usually necessary to include balance valves to produce an' equal pressure drop across each gear set, in addition to lock valves to isolate each side of the system during periods of zero flow. Also, such gear type dividers arenot verysuitable or efficient under pulsatingflow conditions when such balance and lock valves are incorporated in the system.

A flow dividing unit of high volumetric efficiency, with virtually no interflow or cross leakage at the holding or off position of the control valve, and having all the previously named requirements, can be made from two piston type pump-motor units. The term pump-motor unit is intended to indicate adual purpose unit, which is reversible and usable either as a hydraulic pump or a hydraulic motor.

However, a two-unit assembly of the above type will not be satisfactory, if used without a suitable booster means, where the work pressure is more than a small percentage of the available pump pressure. This is due to the locking friction in the units caused by the work pressure being imposed on the discharge side of the units, and which friction is inherent in pump-motor units of the piston type, as will be appreciated by those skilled in the art.

The result of this friction is that such a two-unit flow divider would be very stiff and reluctant to operate unless the work pressure is quite low with relation to the available pump pressure. This is not practical and even with such pressure relationship the units would not operate with the sensitivity required for a practical control system. This deficiency in the otherwise ideally suited type of hydraulic unit can be remedied by applying a booster means which adds extra torque effort to overcome the inherent friction of such units. This has been accomplished by'adding a third piston pump-motor unit to the flow dividing units; the various units being mechanically connected in a certain relationship as well as being hydraulically connected; as shown and described previously herein. By thus positively driving the piston-type hydraulic pumps at constantly equal speeds, and by feeding fluid under pressure separately to the inlet of the pumps from the oneconduit, identical pressureflows from the two pumps to the rams or other work or load devices are assured, and leakage past the pumps in a reverse direction when valve 32 is closed is prevented by the nonleaking or non-pressure-bypassing nature of the pistontype pumps.

While, as previously stated, the flow dividing system herein described has been particularly developed for service in a road builder or land leveler, the utility of the system is not limited to such service, as will be appreciated.

From the foregoing description it will be readily seen that there has been provided such a system as will fully fulfill the objects of the invention, as set forth herein.

While this specification sets forth the present and preferred construction of such system, still in practice such deviations from such detail may be resorted to as do not form adeparture from the spirit of the invention, as defined :by the appended claims.

Having thus described the invention the following is claimed as new and useful, and upon which Letters Patent are desired:

1. In a flow dividing system, a pair of separate hydraulic pumps each including a housing and a drive shaft projecting from one end thereof, a hydraulic motor including a housing and adriven shaft projecting from one end thereof, there being a branched pressure conduit connected to the intakes of the pumps and to the motor, and outlet conduits leading from the pumps for connection to separate hydraulic work members; means connecting the pumps and motor together as a rigid unit with the shafts parallel to each other and the ends thereof in a common plane, and a driving arrangement connecting the ends of all the shafts.

2. A structure, as in claim 1, in which said driving arrangement comprises sprockets on the projecting portions of the shafts disposed in a common plane, and an endless chain embracing and engaging all said sprockets.

3. A structure, as in claim 1, in which said pump and motor connecting means comprises a rigid flat faced mounting plate, means securing the housings of the pumps and motor to the plate and against one face thereof with the projecting portions ofthe shafts extending through openings in the plate and a certain distance beyond the opposite face thereof. A

4. A flow dividing systemcomprising a pair of hydraulic pumps, a hydraulic motor separate from the pumps, means to drive the pumps from the motor at predetermined relative speeds, fluid pressure conduits leading from the outlets of the pumps connected to hydraulic work members, a fluid pressure supply conduit, branches from the supply conduit connected at theirends to the inlets of the pumps, a branch feed conduit leading from the supply conduit to the motor to supply fluid pressure to drive the motor, a reservoir from which the pressure conduit leads, a separate driven pump interposed in the pressure conduit between the branch feed conduit and the reservoir and taking from the latter, a return conduit between the reservoir and pressure conduit and connected to the latter at a point between said pressure conduit and the separate pump, and a control valve interposed in the pressure and return conduits and arranged to selectively control the flow from said separate pump through the pressure and branch conduits to the motor, through the pressure conduit beyond the valve to return conduit, and to close communication between the pressure conduit on opposite sides of the valve and the return conduit.

References Cited in the file of this patent UNITED STATES PATENTS 

